1. Invertebrates

2. Sponges
• Simplest Animal
• Lack symmetry
• Range from a diameter of 1cm to as large as 2m
• Most are bag-shaped and have a large internal cavity
• Most are sessile (they attach themselves firmly to the
sea bottom or submerged surface and stay there for
life)
• Consist of specialized cells embedded in a gel-like
substance called mesophyl
• Resembles chopped fruit in gelatin

3. Sponges
Plankton and other tiny organisms are trapped as
the water moves through the sponges’ body
Waste is carried out the sponges’ as the water moves
out
Sponges are found mostly in warm shallow seas
Some live at great depths
A few are even found in fresh water

5. Sponges
Grouped by into three types based on skeletal
composition
1. Calcareous sponges have spicules (tiny needle
composed of silica or calcium carbonate)

6. Sponge Reproduction
Can reproduce asexually
Can regenerate when cut into pieces
Will reproduce by shedding a piece then it
regenerates into a new sponge
Sexual reproduction can take place
Most sponges are hermaphrodites (produce both
eggs, and sperm)
Egg and sperm are produced at different times so
that self-fertilization is avoided

7. Cnidarians
Diverse group with two main body types:
1. Medusa: free floating jelly like and often umbrella
shaped.
2.Polyp: tube-like and are usually attached to rocks or
other objects

8. Medusa

9. Polyp

10. Cnidarians
Have a gastrovascular cavity
The opening is surrounded by tentacles which have
stinging cells called cnidocytes.
Each cnidocytes has a small barbed harpoon called a
nematocyst
Extracellualr digestion: digestion takes place outside
of the cell. This is where we first see this, but it takes
place in all other species of animals,

11. Cnidarians
Hydrozoans: The most primitive of the cnidarians.
Live in colonies
Life cycle includes both polyp and medusa stages,
Can be both freshwater and marine
 Reproduce asexually by forming a bud
Many have the ability to reproduce sexually
Best known is the Portuguese man of war.

12. Portuguese Man-of-War

13. Cnidarians
Scyphozoans: “True Jellyfish”
Store toxins inside the nematocysts (some species
are extremely potent)
Active predators the catch and sting prey in their
tentacles

15. Phylum Platyhelminthes
Phylum Platyhelminthes-Commonly known as
flatworms
Simple animals, un-segmented bilaterally
symmetrical and 3 cell layers
One body cavity: gut
Some are parasitic
No respiratory or circulatory system
Most can reproduce sexually or asexually
Oxygen and nutrients pass into body through
diffusion

16. Phylum Platyhelminthes

17. Phylum Nematoda
Phylum Nematoda: roundworms
Epidermis secretes hard and flexible cuticle
Head has a few very tiny sense organs and mouth
No respiratory or circulatory system
Bilaterally symmetrical worm-like organism
Reproduce sexually
Most are dioecious (organisms that have either male
or female parts)

18. Phylum Nematoda

19. Phylum Mollusca
Phylum Mollusca: snails, squid, clams, octopuses,
and scallops
Soft bodies usually have a “head” and “foot”
Often have a exoskeleton
Usually have open circulatory system
Have sensors to detect chemicals, vibrations, and
touch
Use the same organ for many functions (for example:
the heart and kidneys are important parts of the
reproductive, circulatory, and excretory systems)

20. Phylum Mollusca

21. Phylum Annelida
Phylum Annelida: segmented worms (earthworms),
leeches
Body usually has bristles
Live in a variety of aquatic and land habitats
Locomotory, respiratory, and exretory organs are
repeated in segments through the body
Share a common nervous system, circulatory system,
and gut
Usually reproduce sexually, but some have the ability
to reproduce asexually

22. Phylum Annelida

23. Phylum Arthropoda
Phylum Arthropoda: spiders, insects, scorpions, and
crawfish
Exoskeleton made of chitin
Segmented body
Segments are sometimes fused into 3 parts: head,
thorax and abdomen
Jointed appendages
Bilaterally symmetrical
Most have a pair of compound eyes
Have an open circulatory system
Most lay eggs

24. Phylum Arthropoda

25. Phylum Echinodermata
Phylum Echinodermata: sea cucumbers, sea urchins,
and starfish
Many have five-fold symmetry
Have a system of internal water filled canals
Live in marine habitats
Have separate male and females
Decentralized nervous system
Skeleton composed of calcium
Have simple but complete digestive gut
Simple radial nervous system

26. Phylum Echinodermata

27. Phylum Rotifera
Phylum Rotifera: microscopic aquatic animals
Soft bodies
Have specialized organ systems and a complete
digestive tract including a mouth and anus
Eat plants or animals through filter feeding
Unusual reproduction can reproduce asexually or
sexually
Bilaterally symmetrical
Have a small brain and nervous system

28. Phylum Rotifera